A substrate processing apparatus is configured to perform specific processes such as a film forming process, an etching process and the like on a substrate to be processed (hereinafter, simply referred to as “substrate”) such as a semiconductor wafer, a liquid crystal substrate or the like.
As for such a substrate processing apparatus, there has been known a plasma processing apparatus, for example. The plasma processing apparatus includes, inside a processing chamber, a lower electrode serving also as a mounting table for mounting thereon a substrate and an upper electrode serving also as a shower head for injecting a gas toward the substrate. Such a parallel plate type plasma processing apparatus is configured to perform specific processes such as a film forming process, an etching process and the like with the use of a plasma generated by applying a high frequency power between both electrodes while supplying a specific gas through the shower head onto the substrate in the processing chamber.
In performing on the substrate specific processes such as a film forming process, an etching process and the like, there has been demanded to improve in-surface uniformity in processing the substrate by making processing characteristics (e.g., an etching rate, an etching selectivity, a film forming rate and the like) uniform in a surface of the substrate.
In such a view, in Japanese Patent Laid-open Application Nos. H8-158072 and H9-45624, there have been proposed techniques for supplying a processing gas of optional composition at an optional flow rate to plural portions on a substrate surface via gas supply lines individually connected with a plurality of gas chambers formed by dividing the inside of the shower head. In accordance with such techniques, the in-surface uniformity in etching the substrate can be improved by locally adjusting a gas concentration on the substrate surface.
A gas used for an actual substrate processing is obtained by mixing plural types of gases, e.g., a processing gas directly participating in a substrate processing, a gas for controlling a deposition of reaction products generated in the substrate processing, a carrier gas such as an inactive gas or the like, and the like. The types of gases are appropriately selected depending on target materials on the substrate or processing conditions. Therefore, there arises a need to perform a flow rate control by using a mass flow controller provided on each of the gas supply lines respectively connected with the gas chambers in the shower head, as disclosed in Japanese Patent Laid-open Application No. H9-45624.
However, in such a conventional configuration, although the gases supplied to plural portions on a substrate surface include common gases, each of the gases supplied from the gas chambers has its own gas supply system and, also, flow rates thereof are individually controlled. Accordingly, a line configuration and a flow rate control in each of the lines become complicated, which results in requiring a large space for the lines and an increased burden of control.
Moreover, an additional gas supply system may be provided in addition to the aforementioned gas supply system to thereby adjust components of the gases supplied to the gas chambers of the processing chamber by adding an additional gas, which is supplied at a preset flow rate from the additional gas supply system, to the gases from the gas supply system. However, when the additional gas is supplied at a very small flow rate (e.g., a few sccm), an inner pressure of a line of the additional gas supply system does not increase rapidly, which lengthens time required for the additional gas to reach the processing chamber via the line of the additional gas supply system. Accordingly, a gas concentration in the processing chamber becomes stable after a lapse of a long period of time, which may deteriorate a throughput.